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PostPosted: Wed Mar 21, 2018 8:40 pm 
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Evening folks

We have just had a ground floor extension built and it was plastered a couple of weeks ago. All dried to a nice light pink.

I did the ceilings with Benjamin moore sure seal rather than a mist coat. (It's like a posh new plaster paint) followed by two coats of their matt emulsion which looked great (at hefty expense)

For the walls I used Johnstone's covaplus vinyl matt for the mist coat. I did it probably 60/40 but it gave better than expected coverage. I finished the walls with two coats of the BM matt emulsion. I used to use contract matt but I had the covaplus to hand and read VM was ok for mist coating? Tin says can dilute by 10%!

I noticed a run on one of the walls having left them 24hrs to dry. On sanding it lightly with 240 grit a section of paint peeled off to bare plaster!!! I tested other parts of the wall with masking tape and in many places it was pulling the paint off.

Out of interest I also tested a subtle part of the top of another wall which I had coated with the sure seal first and the tape also pulled off the paint to bare plaster.

Sadly the affected wall is huge and so I've started the laborious process of scraping the paint off. This is actually harder than I expected and will take a good few hours. No doubt the scraping will leave plenty of dints to fill too.

I can't see any visible issues anywhere else but am worried in weeks to come paint will lift/bubble? I've spent hours on it and the paint costs a fortune.

I didn't think the walls had been over polished by the plasterer and did give them a Hoover off. I didn't use a damp cloth which may be my down fall!

Any suggestions what may have gone wrong?

I can just about cope with the one huge wall to sort but if the rest needs doing I don't know what I'll do. The tape also lifted the bare mist coat elsewhere- doesn't look like the paint soaked in at all tbh.

Bloody kitchen etc all arriving Monday so not much time to sort things out.

Thanks for any suggestions!


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PostPosted: Thu Mar 22, 2018 1:01 am 
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Minibbb wrote:
Evening folks
<snip>
I did the ceilings with Benjamin moore sure seal rather than a mist coat. (It's like a posh new plaster paint) followed by two coats of their matt emulsion which looked great (at hefty expense)

For the walls I used Johnstone's covaplus vinyl matt for the mist coat. I did it probably 60/40 but it gave better than expected coverage. I finished the walls with two coats of the BM matt emulsion. I used to use contract matt but I had the covaplus to hand and read VM was ok for mist coating? Tin says can dilute by 10%!


Evening to you too.

Walls/Johnstone's.
Vinyl paint is OK[*] for mist coating but you must have a perfectly dry wall as it won't allow for any further breathing of the plaster. There again it is no different if you painted with non vinyl and then you gave it a coat of vinyl paint. Anyhow, my two brain cells say this is not the problem.

You diluted the vinyl paint 60/40, what is the 60 and what is the 40? Note that tin says you can dilute by (up to) 10%. What time intervals did you allow between coats?

I would guess a failed mist coat either by it being too thin or overcoated too quickly.

Sure seal
I had to look for the spec. sheet and to my surprise it does for new plaster and plasterboard as well as it does nearly everything else under the sun. Was this a thin runny product or thick like standard paint? Maybe testing with tape is not a good idea. If the paint was to bubble, assuming you let coats dry in full and not touch dry, it could have bubbled by the time you applied the second coat.

Pass, see what the professionals have to suggest.

-----
[*] based on standard waffle from Crown Trade paint.



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PostPosted: Thu Mar 22, 2018 1:38 am 
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OchAye wrote:
Minibbb wrote:
Evening folks
<snip>
I did the ceilings with Benjamin moore sure seal rather than a mist coat. (It's like a posh new plaster paint) followed by two coats of their matt emulsion which looked great (at hefty expense)

For the walls I used Johnstone's covaplus vinyl matt for the mist coat. I did it probably 60/40 but it gave better than expected coverage. I finished the walls with two coats of the BM matt emulsion. I used to use contract matt but I had the covaplus to hand and read VM was ok for mist coating? Tin says can dilute by 10%!


Evening to you too.

Walls/Johnstone's.
Vinyl paint is OK[*] for mist coating but you must have a perfectly dry wall as it won't allow for any further breathing of the plaster. There again it is no different if you painted with non vinyl and then you gave it a coat of vinyl paint. Anyhow, my two brain cells say this is not the problem.

You diluted the vinyl paint 60/40, what is the 60 and what is the 40? Note that tin says you can dilute by (up to) 10%. What time intervals did you allow between coats?

I would guess a failed mist coat either by it being too thin or overcoated too quickly.

Sure seal
I had to look for the spec. sheet and to my surprise it does for new plaster and plasterboard as well as it does nearly everything else under the sun. Was this a thin runny product or thick like standard paint? Maybe testing with tape is not a good idea. If the paint was to bubble, assuming you let coats dry in full and not touch dry, it could have bubbled by the time you applied the second coat.

Pass, see what the professionals have to suggest.

-----
[*] based on standard waffle from Crown Trade paint.


Thanks OchAye, I was hoping you may reply :thumbright:

Sorry to clarify I used about 60% paint to 40% water. I do find with mist coating that despite thoroughly mixing the paint/water you can end up with thicker paint on the roller than you would like.

The room has been about 13 degrees so not the warmest. Could time improve adhesion? I'm seriously fretting more paint will fail albeit the 1/3 of the wall I still have to strip is being pretty hard work to get off! Maybe the tape test isn't such a good idea? With an effective mist coat would tape still lift it or not would you think?

The sure seal is almost like normal paint tbh- went on very well and much better opacity than I expected.

Im hoping to have the rest of the paint off the damaged wall tomorrow and will sand with the palm sander prior to a mist coat with Leyland trade contract matt. No doubt then ill see all the scraper marks ive made ::b



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PostPosted: Thu Mar 22, 2018 2:32 am 
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Minibbb wrote:
Thanks OchAye, I was hoping you may reply :thumbright:

Thank you thank you thank you . I will widen the door frames next in case my head gets stuck ... or amongst the blind I got 1 eye kind of thing :wink:

Quote:
Sorry to clarify I used about 60% paint to 40% water. I do find with mist coating that despite thoroughly mixing the paint/water you can end up with thicker paint on the roller than you would like.

Ahh. Like you, I don't paint for a living so I don't have enough experience to make claims of my own. Plus out of boredom I have read many of the Crown specification sheets (I always wanted to be a geek at something). I think it is mostly Crown paints that can go to 40% added water, most go to 10 or 20% and blah blah the 40% is for highly polished plaster.

In my simpleton chemistry in a tin of paint you got water + colour things + things that make the paint stick. Covaplus has a good reputation here for its opacity (i.e. it has many colour things in it). But when the manufacturer says no more than 10% dilution it means the paint does not have enough sticky/glue things in it ... for a mist coat you need a thin enough paint to penetrate into the plaster but with all its glue things in tact so it can stick to the surface. I think you got a lot of colour on the wall but the paint being too thin did not stick to the plaster.

Anyway, rule of thumb for mistcoating here is to add 20-25% water.

Quote:
The room has been about 13 degrees so not the warmest. Could time improve adhesion? I'm seriously fretting more paint will fail albeit the 1/3 of the wall I still have to strip is being pretty hard work to get off! Maybe the tape test isn't such a good idea? With an effective mist coat would tape still lift it or not would you think?

I make it up here ... I dont know. You have touch dry time (a couple of hours), you have recoating time (say 4 hours) and you have curing time (days). At 13 degrees recoating times would be longer. if you want to understand look back at how quickly you recoated ... because if your mist coat wasn't dry enough your next coat(s) dissolved it completely so it is like you did not ever have a mist coat.

Sorry, I can't tell about masking tape ... I avoid it as much as possible (brings back some nasty memories from I was a teenager).

Quote:
The sure seal is almost like normal paint tbh- went on very well and much better opacity than I expected.

Im hoping to have the rest of the paint off the damaged wall tomorrow and will sand with the palm sander prior to a mist coat with Leyland trade contract matt. No doubt then ill see all the scraper marks ive made ::b

Leave the ceiling alone ... if it turns bad down the road ... toolstation has some thin plastic sheeting rolls you can cover all your new kitchen cabinets with and attack the ceiling. For the rest, use a fine surface filler, sand well the edges so it blends with the rest, and mist coat (AKA prime) the filler before you paint.

Sorry I am not really of much help, I am trying to give you some moral support if nothing else.



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PostPosted: Thu Mar 22, 2018 2:41 am 
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Ah that's interesting it looks like I added too much water! When I try the Leyland Ill stick to about 20% then. I forgot to reply about re-coat times. This week has been a bit of a blur with shifts and trying to paint when I can (i.e here we both are at 0230 hrs on a forum talking about painting :lol: ) Therefore I can't remember exactly but Im sure I left the mist coat overnight and did one coat on the walls in the morning and the other in the afternoon.

I'm deffo leaving the ceiling well alone!

Here is where I got to before I left for work- thankfully not huge amounts left to strip before I can sand it. Guessing I should also remove the paint where the kitchen tiles will be in case the tiles end up falling off ::b

https://ibb.co/k9Mi9c


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PostPosted: Thu Mar 22, 2018 2:55 am 
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Minibbb wrote:
Here is where I got to before I left for work- thankfully not huge amounts left to strip before I can sand it. Guessing I should also remove the paint where the kitchen tiles will be in case the tiles end up falling off ::b

https://ibb.co/k9Mi9c
If you know where the tiles will go paint a couple of centimetres into the tiled area and leave alone and when the tiler arrives attack the rest of the surface with some thick sand paper to scratch it a bit. Looking at the photo it looks so clean. Did by any chance the plasterers do you a favour and PVAed the new plastering for you? I hope not ::b


Last edited by OchAye on Thu Mar 22, 2018 2:57 am, edited 1 time in total.


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PostPosted: Thu Mar 22, 2018 2:57 am 
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OchAye wrote:
Minibbb wrote:
Here is where I got to before I left for work- thankfully not huge amounts left to strip before I can sand it. Guessing I should also remove the paint where the kitchen tiles will be in case the tiles end up falling off ::b

https://ibb.co/k9Mi9c
If you know where the tiles will go paint a couple of centimetres into the tiled area and leave alone and when the tiler arrives attack the surface it with some thick sand paper to scratch it a bit. Looking at the photo it looks so clean. Did by any chance the plasterers do you a favour and PVAed the new plastering for you? I hope not.


Im not sure......? I didn't see him PVA it but theres every chance he may have? He is back in a couple of weeks to do a bit in the hallway so I'll check!


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PostPosted: Thu Mar 22, 2018 2:59 am 
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Minibbb wrote:
Im not sure......? I didn't see him PVA it but theres every chance he may have? He is back in a couple of weeks to do a bit in the hallway so I'll check!


It will be too late. See if you ask him before you paint any more. Paint and PVA do not play together (there is a sticky thread at the top of the P&D forum).



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PostPosted: Thu Mar 22, 2018 9:22 am 
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I haven't used Benjamin Moore or Johnstone's so I can't comment on those specific products but I have always mist-coated with a contract matt, usually Armstead, watered down to 80% paint - 20% water. Those percentages aren't 100% accurate, but as near as I can get using an old pint measuring jug that I nicked off Mrs d'A and carry in the van. I read somewhere that it is better to have too much water than not enough. I leave the mist-coat to dry for about 2 hours and then I paint the walls with the first coat of Vinyl Matt (or Silk, which seems to be making an annoying comeback). I have never had a problem with the paint peeling after using this method.

To fix your specific problem, without having to scrape every wall, it might be worth trying a coat of Zinsser Peel Stop on one of the walls and then painting over it with two coats of your emulsion of choice to see if it also starts to peel. If it doesn't peel then I would paint the rest of the room with a coat of Peel Stop and then repaint. A 2.5 ltr tin of Peel Stop is plenty to cover a whole room, including the ceiling, and it is usually cheaper to buy it on eBay than from any shops. If this doesn't work then you're going to have the aggro of scraping it all off and starting again. I have used Peel Stop several times when I have been asked to decorate a room where the old paint is peeling, usually the ceiling above an en-suite, but also on walls where the previous painter, usually the builder's painter, didn't mist-coat. It has never let me down. Even if there is only a small area that is currently peeling, I will paint Peel Stop over the whole ceiling or wall just to make sure.



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PostPosted: Fri Mar 23, 2018 12:35 am 
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Thanks Tom

I hadn't thought of peel stop! Gardz saved my skin in the other rooms in the house (over old silk which despite sanding still caused issues!)

So far the paint elsewhere hasn't bubbled or lifted so fingers crossed I've got away with the one wall.

All sanded today and wiped down with a damp cloth. will leave overnight and mist Tomo with the contract matt and hopefully we are sorted at last!

Will teach me to use a vinyl matt to mist! Btw OchAye- the plasterer confirmed no PVA so I can only assume a paint fault?



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